New fish feeding deterrents, including a novel sesquiterpenoid heterogorgiolide, from the Brazilian gorgonian Heterogorgia uatumani (Octocorallia, Gorgonacea)

Studies of the Brazilian gorgonian octocoral Heterogorgia uatumani have res ulted in the discovery of two metabolites that inhibit fish feeding under n atural conditions. These are the previously reported eunicellane diterpenoi d, (6E)-2 alpha,9 alpha-epoxyeunicella-6,11(12)-dien-3 beta-ol (1) and a ne w sesquiterpene lactone, heterogorgiolide (2). The structures of I and 2 we re determined by spectroscopic methods and by comparison of spectral data w ith Literature values. Field bioassays of the two compounds, at their natur al concentrations, confirmed that they deter predation by a complex assembl age of reef fishes. This is an unusual observation showing that defenses ar e derived from both sesqui- and diterpenoid metabolites.